Electrical Engineering Dictionary - part 122

(2) the class of computer memory that re-

tains its stored information when the power
supply is cut off. It includes magnetic tape,
magnetic disks, flash memory, and most
types of ROM.

nonvolatile

random-access

memory

(NVRAM)

SRAM or DRAM with non-

volatile storage cells. Essentially each stor-
age cell acts as a normal RAM cell when
power is supplied, but when power is re-
moved, an EEPROM cell is used to capture
the last state of the RAM cell and this state
is restored when power is returned.

nonzero-sum game

one of a class of

games in which the sum of the cost func-
tions of the players is not constant. A num-
ber of players is not limited to two as in
zero-sum games, and in this sense one may
distinguish between two-person and multi-
person nonzero-sum games. Since the objec-
tives of the players are not fully antagonis-
tic, cooperation between two or more deci-
sion makers may lead to their mutual advan-
tage. However, if the cooperation between
the players is not admissible because of in-
formation constraints, lack of faith, or impos-
sibility of negotiation, the game is noncoop-
erative and an equilibrium may be defined in
a variety of ways. The problem of solving
the nonzero-sum game differs from that of
the zero-sum game. The most natural solu-
tion is Nash equilibrium, which is relevant
to the saddle point equilibrium in zero-sum
games. Its main feature is that there is no
incentive for any unilateral deviation by any
one of the players and their roles are sym-
metric. If one of the players has the ability to
enforce his strategy on the other ones, then
a hierarchical equilibrium called von Stack-
elberg equilibrium is rational. Yet another
solution for the player is to protect himself
against any irrational behavior of the other
players and adopt min-max strategy by solv-
ing a zero-sum game, although the original
is nonzero-sum.

NOR gate

a logic circuit that performs the

operation equivalent to the OR gate followed
by the inverter. The output of a NOR gate is
low when any or all inputs are high.

norator

an idealized two-terminal net-

work element for which the voltage across
it and the current through it are determined
by the network to which it is connected.

norm

a vector space

V , a norm is a real-

valued function

N defined on V , satisfying

the following requirements for every

v, w ∈

V and scalar λ:
1.

N(0) = 0 and for v 6= 0, N(v) > 0.

N(λv) = |λ|N(v).

N(v + w) ≤ N(v) + N(w). The most

usual norms are the

, and

∞

norms;

for a vector

x with n coordinates x

, . . . , x

we have

kxk

k=1

kxk

k=1

and

kxk

∞

max

k=1

for a function

f defined on a set E, these

norms become

kf k

|f (x)| dx,

kf k

|f (x)|

and

kf k

∞

= min{r ≥ 0 | |f (x)|
≤ r almost everywhere}.

Given a norm

N, the function d defined by

d(x, y) = N(x − y) is a distance function
on

V . See

normal demagnetization curve

the sec-

ond quadrant portion of the hysteresis loop
generated when magnetic induction (

B) is

2000 by CRC Press LLC

plotted against applied field (

H ), which is

mathematically related to the intrinsic curve;
used to determine the performance of a mag-
net in a magnetic circuit.

normal dispersion

increase of index of

refraction with increasing frequency; tends
to occur near the center of amplifying transi-
tions or in the wings of absorbing transitions.

normal distribution

See

Gaussian

distribution

normal tree

a tree that contains all the

independent voltage sources, the maximum
number of capacitors, the minimum number
of inductors, and none of the independent
current sources.

normal vector

a vector perpendicular to

the tangent plane of a surface. Also, a vec-
tor which is geometrically perpendicular to
another vector.

normalization

(1) the process of refor-

matting a floating point number into a stan-
dard form at the completion of a floating point
arithmetic operation.

(2) the process of equalizing signal ener-

gies, amplitudes, or other features prior to
comparison.

normalized number

a floating-point

number in which the most significant digit of
the significand (mantissa) is non-zero. In the
IEEE 754 floating-point standard, the nor-
malized significands are larger than or equal
to 1, and smaller than 2.

normally closed contact

contact of a con-

tactor that is closed when the coil of the con-
tactor is deenergized and opened when the
coil is energized.

normally closed, time to close

a relay that

is closed when the power to its actuator is off,
but has a time delay to close when power is
removed from the actuator. When power is
applied, the relay immediately opens.

normally open contact

a contact that is

open under normal operating conditions and
closes when an action is initiated in its con-
troller. For a contact that is part of a relay,
the contact remains open when the relay is
deenergized and closes when the relay is en-
ergized.

normally open, time to close

a time de-

lay relay that is open when the power to its
actuator is off. When power is applied to
the actuator, the relay remains open for an
adjustable time delay, after which it closes.
When power is removed from the actuator,
the relay opens immediately.

Northeast blackout

a 1965 failure of

much of the power grid in the northeastern
states of the USA.

Norton theorem

states that the voltage

across an element that is connected to two ter-
minals of a linear, bilateral network is equal
to the short-circuit current between these ter-
minals in the absence of the element, divided
by the admittance of the network looking
back from the terminals into the network,
with all generators replaced by their internal
admittances.

NOT

a Boolean operation that returns the

1’s complement of the data to which it is ap-
plied.

notch

a disturbance of the normal voltage

waveform of duration less than 0.5 cycles,
is of a polarity that is opposite to the wave-
form and is hence subtracted from the normal
waveform with respect to the peak value of
the disturbance voltage.

Noyce, Robert N.

(1927–1990) Born:

Denmark, Iowa, U.S.A.

Noyce is best known as one of the

founders and co-chair of Intel Corpora-
tion, and a developer of the first commer-
cially successful microchip, along with Gor-
don Moore. Noyce began his career with
William Shockley’s short-lived company. He

2000 by CRC Press LLC

and other engineers split with Shockley and
formed Fairchild Semiconductor. Fairchild
was the first of the very successful “Silicon
Valley” high-tech firms. Noyce’s patent on
the microchip was challenged by Jack Kilby
and Texas Instruments. A court ruled in favor
of Noyce, although it is commonly accepted
that the original ideas were Kilby’s.

NPO

See

negative-positive-zero

NPR

See

noise power ratio

NRC

the Nuclear Regulatory Commis-

sion, a US regulatory body which oversees
civilian power reactors.

NRD

waveguide

See

nonradiating

dielectric waveguide

NRE

See

nonrecurring engineering

NTSC

See

National Television System

Committee

NuBus

an open bus specification devel-

oped at MIT and used by several companies.
It is a general-purpose backplane bus, de-
signed for interconnecting processors, mem-
ory, and I/O devices.

nuclear fuel

fissile material, including

natural uranium, enriched uranium, and some
plutonium prepared for use in a nuclear reac-
tor.

nuclear fuel management

the process of

managing the degree of enrichment, the tim-
ing of insertion into the core, and the place-
ment and possible relocation of fuel within
the core during the lifetime of the fuel.

nuclear magnetic resonance

the phe-

nomenon in which the resonant frequency of
nuclear spin is proportional to the frequency
of an applied magnetic field. See

magnetic

resonance imaging

nuclear power plant

a thermal electric

power plant in which the heat for steam tur-
bines is produced by nuclear fission.

nuclear reaction

a reaction which causes

changes in the nucleus of an atom, thus
changing elements to another element or iso-
tope, usually with the release of energy.

nuclear reactor

(1) an apparatus designed

to facilitate, contain, and control a nuclear
chain reaction.

(2) any heat-producing array of fissile ra-

dioactive materials constructed so as to pro-
duce a controlled chain-reaction.

null

a point on the radiation pattern that

corresponds to zero or minimum values.

null controllability

a dynamical system

that is controllable to zero end state.

many cases, null controllability is equiva-
lent to controllability. This is always true
for linear finite-dimensional continuous-time
dynamical system.

However, in discrete

case, controllability may be the stronger no-
tion than null controllability. In this case,
the two concepts are equivalent if and only
if rank

(A) = n. For dynamical systems

with delays, these two notions are essentially
different. For infinite-dimensional systems
the relations between null controllability and
controllability depend on the properties of the
semigroup

S(t) generated by the operator A.

null space

the set of vectors that are or-

thogonal to every vector of a set forming vec-
tor space. For an

(n, k) code, the dimension

of the null space is

n − k.

null space of the Jacobian

the subspace

N(J ) in R

of joint generalized velocities

that do not produce any end-effector velocity,
in the given manipulator posture. Nonzero
subspace for a redundant manipulator allows
to handle redundant degrees of freedom. The
existence of nonzero subspace allows for re-
dundant manipulator to generate internal mo-
tions of the manipulator structure that do not

2000 by CRC Press LLC

change the end-effector position and orienta-
tion. As a consequence allows manipulator
reconfiguration into more dexterous postures
for execution of a given task.

null steering

a technique used to form

an antenna’s radiation pattern in such a way
that there is no radiation in the direction of
an interfering signal.

This technique has

been used with great success, for example,
where CDMA systems have been overlaid
with fixed microwave communication sys-
tems.

null-to-null bandwidth

the width of the

main lobe of a signal or system transfer func-
tion in the frequency domain.

nullator

an idealized two-terminal net-

work element that conducts no current and
yet maintains zero volts across itself. This
element is often used to represent a virtual
connection.

number system

the representation of

numbers as a sequence of digits with an inter-
pretation rule which assigns a value to each
sequence. The conventional number systems
are fixed-radix and positional systems, where
the digit in position

i has a weight of r

, where

r is the radix.

numerical aperture (NA)

a parameter de-

scribing the light-gathering capacity of an op-
tical fiber. It is defined as the sine of half the
maximum angle of light acceptance into the
fiber

NA =

√

− n

where

is the refractive index of the core,

and

is the refractive index of the cladding.

Also used as a measure of the maximum

angle of the cone of light entering or emerg-
ing from an optical fiber.

numerical methods

methods useful for

obtaining quantitative solutions of electro-
magnetic and microwave problems that have
been expressed mathematically, including

the study of the errors and bounds on errors
in obtaining such solutions.

NUREG

a contraction for Nuclear Regu-

lations, which are published by the NRC.

NVRAM

See

nonvolatile random-access

memory

nybble

See

nibble

Nyquist A/D converter

A/D converter

that samples analog signals that have a max-
imum frequency that is less than the Nyquist
frequency. The Nyquist frequency is defined
as one-half of the sampling frequency. If a
signal has frequencies above the Nyquist fre-
quency, a distortion called aliasing occurs.
To prevent aliasing, an antialiasing filter with
a flat passband and very sharp roll-off is re-
quired.

Nyquist band

for pulse (or quadrature)

amplitude modulation, the frequency band
which is the support of the Nyquist pulse
shape. For a symbol rate of 1

/T , the Nyquist

band is the interval

−1/(2T ) to 1/(2T ).

Nyquist criterion

in analog-to-digital

conversion, the stipulation that the bandwidth
of the sampling frequency must be greater
than twice the bandwidth of the frequency of
the signal being sampled.

Nyquist frequency

See

Nyquist rate

Nyquist I criterion

the Nyquist I criterion

for zero inter-symbol interference states that
if

h(t) is the signaling pulse and the symbol

period is

T , then we must have h(kT ) = 1

for

k = 0 and 0 for k 6= 0, where k is an

integer.